1. Field of the Invention
The present invention relates to dusting powders of the type used for lubricating medical apparatus and gloves used in medical, industrial and consumer applications. More particularly, the invention has to do with absorbable dusting powders made from starches having reduced protein content and a low level of carboxyl groups generated through the slight oxidation of hydroxyl groups. For some applications, other hydroxyl groups are cross-linked using a relatively low level of phosphorus oxychloride (POCl.sub.3).
2. Description of Related Art
Dusting powders used by the medical profession have been associated with numerous problems. Such powders have traditionally been based on talc. However, it has been discovered that talc causes granulomas in the body. Talc also has come under increasing scrutiny as possibly containing asbestos, a carcinogenic substance. While pure mineral talc is composed of a group of hydrous magnesium silicates, commercial talc has varying compositions depending on the source and method of production. Some of these compositions may be contaminated with asbestos.
Talc has effectively been replaced by starch-based powders, but the starch-based powders have a number of disadvantages too. The use of starch has been associated with peritonitis flowing from the use of corn starch on or in surgeons' gloves and has been associated with infections which occur from glove-borne particles during optical surgery which may cause the cornea to turn opaque. Microbial problems are associated with starch because it is an excellent nutrient medium for virtually all vegetative bacteria such as various pathogenic microorganisms.
Despite the aforementioned disadvantages associated with starch-based powders, they are still used by the medical profession because starch is an inexpensive and readily available raw material. There is a need, therefore, for improved starch dusting powders which overcome many of the foregoing problems.
Starch-based dusting powders which are applied to the surface of surgical gloves and other medical apparatus (e.g. examination gloves, tubing, catheters and drains) which may be exposed to internal parts of the body, such as the peritoneal cavity during surgery, must presently meet strict United States Pharmacopoeia (USP) standards for Absorbable Dusting Powders. These standards are published by the United States Pharmacopeial Convention, Inc., 12601 Twin Brook Parkway, Rockville, Md. 20852 USA. All references to the USP or to USP Standards are to the official standards from Jan. 1, 1990 entitled "USP XXII, NF XVII, The United States Pharmacopeia, The National Formulary." The USP standards presently require cross-linking of the starch to prevent gelatinization which would otherwise occur during sterilization when an autoclave is used. New methods of sterilization employing gamma radiation, however, are expected to bring about changes in the USP requirements.
Epichlorohydrin can be used for cross-linking as disclosed in U.S. Pat. No. 4,853,978 to Stokum. The patent relates to antimicrobial medical gloves which can be coated with epichlorohydrin cross-linked corn starch. The starch serves as an antimicrobial agent and a donning assist. The starch powder is believed to be bioabsorbable if left in a wound site. In some applications, antimicrobials (e.g., compositions having fungicidal, bactericidal and/or bacteriostatic properties) having an affinity for the cross-linked starch can be absorbed on the starch.
When epichlorohydrin is used for cross-linking, there is some risk that residual quantities of toxic chlorohydrins can remain in the product. Thus, alternative types of absorbable dusting powders have been developed. U.S. Pat. No. 4,540,407 to Dunn, for example, discloses the use of a polyol powder which also avoids the problem of starch peritonitis.
A chitin-derived, finely divided biodegradable powder is described in U.S. Pat. No. 4,064,564 to Casey for use as a lubricant on surgical gloves. Derivatized chitin, however, is believed to be expensive relative to modified starch and is difficult to obtain in commercial quantities.
Other medical lubricants are disclosed in U.S. Pat. No. 4,773,902 to Lentz et al. which is directed to the use of oxidized cellulose, and U.S. Pat. No. 4,152,783 to Choski which is directed to a surgeon's glove provided with a sodium bicarbonate powder.
It has now been discovered in accordance with the present invention that a new modified starch having reduced-protein content can be prepared which avoids many of the problems associated with prior art products. The starch is modified by treatment with sodium hypochlorite to remove protein, oxidize some of the hydroxyl groups and whiten the product. The hypochlorite treated starch can be washed with water to reduce residual protein further, and/or it can be washed with pyrogen-free water to reduce pyrogen content (and reduce residual protein further) if desired. As another option, the hypochlorite treated starch, before washing, can be cross-linked with POCl.sub.3 at a low level to allow better assimilation while meeting USP Standards. The use of POCl.sub.3 for cross-linking avoids any risk of residual chlorohydrins associated with the use of epichlorohydrin.
U.S. Pat. No. 4,562,086 to Smolka et al. discloses a modified starch for use in food applications which is prepared by etherification with an alkylene oxide followed by cross-linking. Phosphorus oxychloride is disclosed as a cross-linking agent. Treatment of corn starch with hypochlorite is disclosed in U.S. Pat. Nos. 2,070,776 to Bochskandl, 2,951,776 to Scallet et al. and 2,989,521 to Serti et al. The Serti et al. patent describes a process whereby starch is first cross-linked with epichlorohydrin followed by treatment with sodium hypochlorite. These patents do not disclose the processing conditions, or the products of the present invention and none of them relate to the preparation of modified starches for medical uses.